1. Field of the Invention
This invention relates to Colour Enhancing lenses, particularly to such lenses having an integrated visible light transmission, with respect to CIE (Commission Internationale De L'Eclairage) illuminant C, of less than 40% T, referred to hereafter as sun lenses.
2. Description of the Prior Art
In addition to attenuating the overall level of light reaching the eye, sun lenses for use in sunglasses often distort the spectral composition of the transmitted light to provide various effects. Recently much attention has been paid to sun lenses that block or markedly attenuate ultra violet light up to a wavelength of 380 nm. Research has also indicated that light components of even longer wavelengths may also be beneficially attenuated. Accordingly, sun lenses are now available which have a pronounced amber coloration and block blue light in addition to ultra violet light. Such sun lenses have a transmission curve which allows a gradual increase in transmittance as the wavelength increases above 450 nm. This means that blues and greens are severely attenuated compared with yellows and reds.
It is now believed that it is only blue light with a wavelength of less than 450 nm that causes harm to the eye and the present invention seeks to provide a lens which selectively attenuates blue and red light to a lesser extent than prior art lenses, thereby providing a color enhancing lens.